In recent years, next-generation automobiles such as an electric car (EV), a hybrid car (HV) and a plug-in hybrid car (PHV), for which reduction in carbon dioxide and less dependency on petroleum are expected, have been actively developed. Large current is frequently flown in these automobiles, and in order to prevent occurrence of secondary damages such as fire, electric leakage and electric shock, an apparatus for breaking current has come to be required. As such an apparatus, a gas-pressure circuit breaker is known in which gun powder or the like is caused to explode or ignite, and pressure generated is used to break an electronic circuit (Patent Document 1, for example).
An inflator-using gas-pressure circuit breaker installed in automobiles has to meet requirements of the ISO12097 test or tests peculiar to automobile manufacturers in accordance with ISO12097. For example, ISO12097-3 requires an impact test at −35° C., 23° C. and 85° C. Further, as stipulated in JISD204 (JIS standards for automobile parts), when an extremely cold area is taken into consideration, a low-temperature test at −30° C. or −40° C. is required. In order to satisfy such requirements, in a gas-pressure type circuit breaker case for automobiles, metals or ceramics are used. However, in order to reduce the weight of an automobile to attain fuel saving, it is required to replace a metal and ceramics constituting elements by a resin (i.e., fabrication of resin parts). In fabricating resin parts, common engineering plastics having a resistance to heat of 100° C. or higher can withstand the test requirements at 85° C. At the same time, it is required to satisfy test requirements at low temperatures of −35 to −40° C. In addition, a high degree of flame retardancy may be required just in case of ignition.